Explicitly wrap main thread in test_main.cc.

Bug: webrtc:9714
Change-Id: I6ee234f9a0b88b3656a683f2455c3e4b2acf0d54
Reviewed-on: https://webrtc-review.googlesource.com/97683
Reviewed-by: Tommi <tommi@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24560}

test/test_main.cc

@@ -10,6 +10,7 @@
 
 #include "rtc_base/flags.h"
 #include "rtc_base/logging.h"
+#include "rtc_base/thread.h"
 #include "system_wrappers/include/field_trial_default.h"
 #include "system_wrappers/include/metrics_default.h"
 #include "test/field_trial.h"
@@ -87,6 +88,10 @@ int main(int argc, char* argv[]) {
 
   rtc::LogMessage::SetLogToStderr(FLAG_logs);
 
+  // Ensure that main thread gets wrapped as an rtc::Thread.
+  rtc::ThreadManager::Instance()->WrapCurrentThread();
+  RTC_CHECK(rtc::Thread::Current());
+
 #if defined(WEBRTC_IOS)
 
   rtc::test::InitTestSuite(RUN_ALL_TESTS, argc, argv,